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I have been gifted a couple of these TDA7293 Power Amplifier boards, and I need to give power to them. Description says

*DC power supply: positive and negative 25-45V
*The power of the transformer: 100w-200w

The DIY Audio forums talk about using a huge transformer + rectifier board for these amps. Can I use SMPS instead? The SMPS will be lighter than the transformer.

If SMPS can substitute the transformer, I must use two SMPS and connect back to back or a single SMPS with + and - is available? And is the current rating different for SMPS or same as transformer? Thank you.

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  • \$\begingroup\$ Any specific SMPS you have identified? Datasheet or link would help. \$\endgroup\$ – Anindo Ghosh Nov 7 '12 at 8:24
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As long as it meets the voltage/power ratings, you can power it with whatever you like.

A transformer by itself is not a "power supply", an SMPS uses a transformer too, just at a higher frequency which makes it more efficient/smaller. What they are referring to on the DIY Audio forums is a "linear supply", which is more basic but easier to make less noisy than an SPMS so often used for audio. Ratings work the same for either type.

An SMPS can come with whatever voltage outputs you desire, there are plenty of dual rail (positive and negative) supplies out there.

If the SMPS is a good quality and quiet (check datasheet) then there is no reason you can't use it to power your amp.

The TDA7293 can supply up to 100W into 8 ohm. These boards specify 85W however so stick with that rating (or below). To find out the average current needed into 8 ohms for this wattage, the formula is sqrt(W/R) = sqrt(85/8) = 3.26A. The amplifier is not 100% efficient though so you need a higher input wattage to reach this level of output.

What supply depends on how hard you want to drive the boards, but something like they recommend is a good idea, e.g. +/- 30V 150W supply.

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  • \$\begingroup\$ Thanks very helpful sir. Any suggestion how much + - voltage and current is needed for two amplifiers that is left and right channels 85 watts each like this amplifier for 8 ohm speaker? Or how to calculate, I will then calculate myself, not to bother you. \$\endgroup\$ – ExcitingProjects Nov 7 '12 at 9:51
  • \$\begingroup\$ @Oli Glaser I'm a little bit surprised that you didn't mention the noise problems that most "audiophiles" complain about when talking about SMPS systems. \$\endgroup\$ – AndrejaKo Nov 7 '12 at 10:15
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    \$\begingroup\$ @AndrejaKo - I hinted at it with the mention of "easier to make less noisy". There is plenty of high quality audio gear out there that uses switching supplies and works just as well as linear powered gear, it just needs a bit more attention to possible noise problems. \$\endgroup\$ – Oli Glaser Nov 7 '12 at 10:36
  • \$\begingroup\$ @ExcitingProjects - see edits \$\endgroup\$ – Oli Glaser Nov 7 '12 at 10:39
  • \$\begingroup\$ Thank you very much! This is very helpful. Now search begins for nice + - SMPS but not very costly! \$\endgroup\$ – ExcitingProjects Nov 7 '12 at 10:44

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